How-To Geek

Are Modern Computers Still Vulnerable to Damage via Magnets?

It’s such an oft repeated warning that it’s firmly embedded in nerd lore: bring a magnet anywhere near your precious computer and suffer the dire consequences. But is true? Is your computer one run in with a novelty magnet away from digital death?

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-drive grouping of Q&A web sites.

The Question

Although the anti-magnet rule has been repeated so often as to be law, is it actually a hard and fast rule of hardware safety? SuperUser reader Aequitarum Custos wanted to get to the bottom of it all:

When I first started using computers, law of the land in computer class was never bring magnets near anything computer related, lest you lose all your data or screw up your monitor.

Now I am pretty sure magnets will still royally mess up a standard hard drive, and I know for a fact they screw up a CRT monitor.

Though I am also pretty sure they do not screw up a LCD monitor?

Now I have my phone which uses magnets to determine if it’s docked, and it made me wonder.

Is it the power of the magnet preventing data loss or the sheer fact that whatever memory type in the phone is immune to it?

What about ear buds, as I know those have tiny magnets in them. Are those capable of damaging any electronic device currently in use?

I’m wondering if I’m being paranoid, but I really am not sure what magnets will damage and what they won’t!

Is there a list, or rule of thumb for determining what will be hurt by magnets and what won’t be?

Anyone who ever turned on a desk fan near or atop their old CRT monitor can certainly attest that something was happening, as indicated by the wild pattern of rainbows that erupt across the screen, but was that something permanent damage?

The Answers

SuperUser contributor Synetech explains:

A list or rule? Sure, anything that uses electro-magnetism to function could, and would be affected by magnets. The question is what the detrimental effects, if any, would be and how strong and close do the magnets need to be. Generally the two most questioned items are the monitor and disk drives.

LCD/LED monitors are not generally susceptible to magnetic interference like CRTs are because they function completely differently (remember, CRTs use magnets to deflect the electron beam, so an external magnet would obviously mess with that).

Hard-drives are also not affected by magnets because of the way they function. You can research the details on how hard-drives work for a more thorough understanding, but the easy answer is that there is a very powerful magnet inside each hard-drive that controls the read-write head’s movement. That’s why some people like to rip open dead drives to get at the sweet, gooey super-strong magnet inside. If that magnet that is inside the drive, right beside the platters, and it doesn’t wipe them, then any magnet that you are likely to have around isn’t going to.

As for flash drives, they are a different technology altogether so they are not going to get erased.

There is one component however that is indeed affected by magnets that most people miss: cables. While many cables are shielded, some are not and thus susceptible to a magnetic field. For example, a cable connecting the sound card to the speaker may be shielded, but the little cable connecting the CD/DVD drive to the sound card usually isn’t and ingress of a magnetic field could cause interference. Or, while rounded IDE cables (especially for IDE133) are usually shielded, ribbons usually aren’t and even at speeds of 66/100 could be affected enough to cause some corruption or at least reduce performance due to re-tried reads/writes.

I would say that modern systems are not really vulnerable anymore because as time progresses, science and knowledge advances, but unfortunately that’s not sufficient. While that may be true, in the old days things were done right a lot more than today with all the cut corners and cost-reducing measures (eg NVIDIA’s “Bumpgate”).

Anyway, the point is that when it comes to modern computers (I’m counting floppy disks as not-modern), you don’t really need to worry about magnets. You can breath a sigh of relief. :)

While that answers the meat of the inquiry, you’d have to be wildly negligent with an extremely powerful magnet to cause any real damage, contributor dmckee offers an example of the effects of working around a very powerful research magnet:

I recall sitting at a computer on a major particle physics experiment when the big (10x5x3 meters, >100 tons) dipole magnet was being tested about 40 meters away. As they ramped it up the display would twist to one side by about 10 degrees. Hit “degauss” on the monitor front panel, ::blur:: then return and all would be well. Later, they’d ramp down, and the monitor would twist the other way…good times. Leave you wallet in your pocket and walk into the hall while they were doing that and you’d loose the data on the magnetic stripes on all your cards…bad times.

If a magnet that powerful sitting next to the monitor and computer tower couldn’t permanently decommission the machine, then surely a magnetic business card absentmindedly slapped on the side of a computer case is little case for alarm.

Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.


Jason Fitzpatrick is a warranty-voiding DIYer who spends his days cracking opening cases and wrestling with code so you don't have to. If it can be modded, optimized, repurposed, or torn apart for fun he's interested (and probably already at the workbench taking it apart). You can follow him on if you'd like.

  • Published 09/20/12

Comments (16)

  1. r

    …over the years I’ve acquired quite a bunch of actuator plates that I use like fridge magnets

  2. Doug

    An alternating magnetic field may induce a current flow in a cable nearby, but a stationary magnet induces no current except a slight amount as it is brought near, or moved away. (and you have to move it pretty quickly to notice the effect)

  3. Bigtech

    The warning about magnets is quite old…but generally speaking, your storage media was what was vulnerable. Even a HD is semi vulnerable but over the years the tolerance has been oimproved. NO what would really get ya is ye olde floppy disks and super disks.. YOu remember those Zipdisks, SUperdisks, 3.5″ disks, heah, leaving a magnet on one of the could not so much wip[e the data as just corrupt it.

  4. evenzak

    What about phones? I used to have one of those metal disk mounts on my dumb phone that would stick to a magnetic car dock, but I’m afraid to use it on my smartphone. Would a powerful rare earth magnet harm my Galaxy S2? Or am I the paranoid one?

  5. Bazooka

    @evenzak It shouldn’t do anything too bad. The Galaxy S2 uses flash memory.

  6. NSDCars5

    And a netbook with a Western Digital mechanical hard drive, Intel Atom N450, Intel Wireless 1000 B/G/N, no disc drive, and a small sound card from Realtek? Yes, I’m officially paranoid.

  7. mad.madrasi

    @Bazooka – what about the microSD card mate?

  8. benone

    @mad.madrasi – the SD and microSD is essentially the same technology as the USB flash drive – and not bothered by magnets.
    @Evnzak magnets will not affect your Galaxy, or any other current smart phone.

    I do remember wiping floppy disks by putting the disks near or under an old mechanical ringer desk telephone. And having the magnetic paperclip holders banned from the office. To the best of my knowledge, no current technology – including smart phones is going to be affected by normal magnets – That includes ANY magnet that you could get, not the super lab magnets in the comment above.

  9. Tasmin

    A few weeks ago I was sitting on the couch with my laptop beside me and working on my sewing machine on the coffee table. I use a magnetic pin holder when sewing, and at one point I moved the pins right up against the edge of the laptop. The screen blanked, the laptop made a weird noise, then went completely dead, and my heart stopped. I practicality threw the pins across the room and a few seconds later the machine recovered without rebooting. It has never done that again, before or since, but I make darn sure to keep the magnet away from the laptop now just in case. No need to tempt fate.

  10. sirius

    I wonder if the magnetic pin holder affected a switch rather than a component. Was it anywhere near the button for hibernating the laptop or something like that? Older mechanical switches wouldn’t be affected by a small magnet, but electronic switches, or what they’re connected to, might have been what reacted to the magnet.

    I bet those few seconds lasted several minutes. :-)

  11. Squarepants

    My own paranoia with personal identity theft…when it’s time to throw out an old credit/debit card, I take one of those “bucky balls” and pass it over the magnetic strip vigorously…just before I scrape the strip with the scissor, cut it into microscopic slivers, and put into several different waste receptacles. Paranoid much? Yeah.

    Oh yeah, the question….does the magnetic strip get scrambled??

  12. Kevin

    A startup I worked for in the 80’s kept a tape eraser — basically an electromagnet that you’d use to wipe tapes clean of all data. We had strict rules about where to use and where to NEVER use it (near any floppy or hard disks). Not everybody understood the potential dangers. In the early 90’s, I had a salesman working at my startup who told a story of a customer he had in the past who used to store his 8″ floppies — anybody remember those? — by sticking them on the side of a filing cabinet with a magnet!!! My colleague had to explain to his customer why that was a bad idea.

  13. Sean

    Another thing that I would like to point out is that many computer cases are made out of steel and thus act like a kind of primitive/accidental Faraday cage.

  14. Dek

    Some years ago I wanted to erase/corrupt some data on some old 3.5 floppies. Using a very strong magnet I wiped it across the discs many times to no effect. Ended up using a hammer!

  15. Sol

    I tried this too and ended up using a magnet like a hammer

  16. Jim Wright

    “A moving charge generates a magnetic field.”; and a moving magnet induces an electric current (meaning a ‘moving charge’). A solenoid generated electro-magnet, using AC, would be a moving magnetic field.

    A PM placed against the face of an old fashioned TV tube should distort the video.


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